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Don't bother to attach column name lists to RowExprs of named types.

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If a RowExpr is marked as returning a named composite type, we aren't
going to consult its colnames list; we'll use the attribute names
shown for the type in pg_attribute.  Hence, skip storing that list,
to save a few nanoseconds when copying the expression tree around.

Discussion: https://postgr.es/m/2950001.1638729947@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2022-03-17 18:25:44 -04:00
parent ec62cb0aac
commit d7b5c071dd
4 changed files with 14 additions and 15 deletions
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6
src/backend/optimizer/prep/prepjointree.c
View File

@ -2279,8 +2279,8 @@ pullup_replace_vars_callback(Var *var,
* If generating an expansion for a var of a named rowtype (ie, this
* is a plain relation RTE), then we must include dummy items for
* dropped columns. If the var is RECORD (ie, this is a JOIN), then
* omit dropped columns. Either way, attach column names to the
* RowExpr for use of ruleutils.c.
* omit dropped columns. In the latter case, attach column names to
* the RowExpr for use of the executor and ruleutils.c.
*
* In order to be able to cache the results, we always generate the
* expansion with varlevelsup = 0, and then adjust if needed.
@ -2301,7 +2301,7 @@ pullup_replace_vars_callback(Var *var,
rowexpr->args = fields;
rowexpr->row_typeid = var->vartype;
rowexpr->row_format = COERCE_IMPLICIT_CAST;
rowexpr->colnames = colnames;
rowexpr->colnames = (var->vartype == RECORDOID) ? colnames : NIL;
rowexpr->location = var->location;
newnode = (Node *) rowexpr;

1
src/backend/optimizer/util/var.c
View File

@ -809,6 +809,7 @@ flatten_join_alias_vars_mutator(Node *node,
rowexpr->args = fields;
rowexpr->row_typeid = var->vartype;
rowexpr->row_format = COERCE_IMPLICIT_CAST;
/* vartype will always be RECORDOID, so we always need colnames */
rowexpr->colnames = colnames;
rowexpr->location = var->location;

6
src/backend/rewrite/rewriteManip.c
View File

@ -1424,8 +1424,8 @@ ReplaceVarsFromTargetList_callback(Var *var,
* If generating an expansion for a var of a named rowtype (ie, this
* is a plain relation RTE), then we must include dummy items for
* dropped columns. If the var is RECORD (ie, this is a JOIN), then
* omit dropped columns. Either way, attach column names to the
* RowExpr for use of ruleutils.c.
* omit dropped columns. In the latter case, attach column names to
* the RowExpr for use of the executor and ruleutils.c.
*/
expandRTE(rcon->target_rte,
var->varno, var->varlevelsup, var->location,
@ -1438,7 +1438,7 @@ ReplaceVarsFromTargetList_callback(Var *var,
rowexpr->args = fields;
rowexpr->row_typeid = var->vartype;
rowexpr->row_format = COERCE_IMPLICIT_CAST;
rowexpr->colnames = colnames;
rowexpr->colnames = (var->vartype == RECORDOID) ? colnames : NIL;
rowexpr->location = var->location;
return (Node *) rowexpr;

16
src/include/nodes/primnodes.h
View File

@ -1052,15 +1052,13 @@ typedef struct ArrayExpr
* than vice versa.) It is important not to assume that length(args) is
* the same as the number of columns logically present in the rowtype.
*
* colnames provides field names in cases where the names can't easily be
* obtained otherwise. Names *must* be provided if row_typeid is RECORDOID.
* If row_typeid identifies a known composite type, colnames can be NIL to
* indicate the type's cataloged field names apply. Note that colnames can
* be non-NIL even for a composite type, and typically is when the RowExpr
* was created by expanding a whole-row Var. This is so that we can retain
* the column alias names of the RTE that the Var referenced (which would
* otherwise be very difficult to extract from the parsetree). Like the
* args list, colnames is one-for-one with physical fields of the rowtype.
* colnames provides field names if the ROW() result is of type RECORD.
* Names *must* be provided if row_typeid is RECORDOID; but if it is a
* named composite type, colnames will be ignored in favor of using the
* type's cataloged field names, so colnames should be NIL. Like the
* args list, colnames is defined to be one-for-one with physical fields
* of the rowtype (although dropped columns shouldn't appear in the
* RECORD case, so this fine point is currently moot).
*/
typedef struct RowExpr
{